1. Fields of the Invention
The present invention relates to a magnetic positioning device, and more particularly, to a magnetic positioning device for a hand tool so as to magnetically attract an object to the hand tool.
2. Descriptions of Related Art
The conventional hand tool known to applicant is disclosed in U.S. Pat. No. 4,753,142, and a power-driven screwing head is provided and includes a device for automatically uncoupling the screwing head when a specified depth of penetration of a screw into a workpiece is attained. The head includes a shank adapted to be driven in rotation in either sense having an end portion defined by a wall of annular cross-section defining a seat. A plurality of radial bores are defined through the wall. The shank further includes a member projecting from the shank. A screwdriver bit has two ends, one of which is received in the seat. A sleeve surrounds at least the end portion of said shank, and is movable longitudinally of the shank. The sleeve has an upper and a lower end, wherein the lower end is adapted to be rested on a surface of the workpiece in use for driving in a screw. The sleeve defines an internal surface which includes along its axial length an upper zone, a recessed portion and a lower zone. The recessed portion is of larger diameter than the adjacent zones. A coil spring is arranged between the member on the shank and the upper end of the sleeve. A plurality of locking balls each are received in a respective one of the radial bores in the shank seat. The locking balls are movable radially in the bores so that the balls are held in engagement between the upper zone and the screwing head when the shank is being driven in one sense to drive a screw in, and the balls are held in engagement between the lower zone and the screwing head when the shank is being driven in the opposite sense in order to remove the screw, and the balls move radially out of engagement with the screwing head when the recessed portion of the sleeve is aligned with the bores.
However, when the user uses the blade part of the screwdriver bit to rotate the object, the sleeve does not have a proper device to prevent the blade part from being separated from the object. That is to say, the object may easily drop on the ground. Furthermore, the sleeve has a smooth outer surface which can be slippery when grease attached on the sleeve or the user's hand.
The present invention intends to provide a magnetic positioning device for a hand tool so as to magnetically attract an object to the hand tool, such that the shortcomings mentioned above are eliminated.